Voltage regulator



Oct. 20, 1953 H. FRIEDMAN VOLTAGE REGULATOR Filed June 30, 1950 -2 Sheets-Sheet 1 3mm HERBERT FRIEDMAN Mme. IoDOmIP hzmmmao O VOLTAGE ACROSS TUBE H. FRIEDMAN Oct. 20, 1953 2 Sheets-Sheet 2 Filed June 50, 1950 E R T m. M N E G O R mE HR ..U 5 5 DR HNP 9: W H 1 W O M W. mo UST G QA R 0 5 5 0 5 2 w 7 5 w n a b w m N E m .M W Y@ H 5 O '0 m8 L Y E H 5 0 O 6 .M W L E H w E R ,4 U v P FIRING VOLTAGE 3mmm HERBERT FRIEDMAN A95 it xrfonnsvs Patented Oct. 20, 1953 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to voltage regulation in general and to a novel corona discharge voltage regulation tube filling material in particular.

With greater particularity, and with apparatus described herein, the present invention provides regulation of high voltage over a wide range by means of a diode type electron discharge device having electrodes separated by l pending application, Serial No. 787,263, dated November 21, 1947, entitled Voltage Regulator, now U. S. Patent No. 2,523,287, issued Sept. 26, 1950.

In applications having low current consumption, the (non-linear) corona discharge tube is used normally in connection with a simple series voltage dropping resistance (linear) element. In applications having high current consumption the tube is employed in a high impedance circuit as a means for obtaining a reference potential for the control of a series type hard tube regulator circuit. In either application the corona discharge tube is designed to operate in a confined region of its voltage-current characteristics,

known to the art as the corona discharge region.

It is accordingly an object of this invention to provide new filling media for a voltage regulator tube of the foregoing type.

It is another object of this invention to provide various filling media for corona discharge regulator tubes employed in series type circuits for operation over a wide range of input voltage.

Other and further objects and features of the present invention will become apparent on careful consideration of the following detailed description when taken together with the accompanying drawings in which:

Fig. 1 shows a cross-sectional view of a corona discharge regulator tube exemplary of the operating principles and structures involved in the present invention.

Fig. 2 shows current-voltage characteristics typical of the operation of diode type regulator tubes over extended current ranges.

Figs. 3 and 4 show typical circuits wherein regulator tubes are employed.

Figs. 5 and 6 show curves characteristic of the operation of regulator tubes employing filling media in accordance with the teachings ofthe present invention.

Referring now to Fig. 1 there is illustrated in cross section, a corona regulator tube It] employing a filling medium of a new composition in accordance with the teachings of the present invention. As exemplified, the tube comprises two electrodes; an outer cathode cylinder ll made from any suitable metal such as stainless steel or copper, and an inner coaxial anode cylinder or rod I2 also made of any suitable metal such as either of the above. The electrodes are sealed at their adjacent ends by means of glass insulating caps l3 and I4 or the like to form a gastight chamber between the electrodes. This chamber is filled to a predetermined pressure with a gaseous medium in accordance with the teachings of the present invention. Attached to the anode cylinder l2 at one end thereof through cap l4 to provide an electrical connection thereto is a flexible lead 15.

As aforementioned, regulation of high voltages by a diode type of tube as exemplified herein is accomplished with operation of the tube in the corona discharge region of its voltage-current characteristics. A typical plot of characteristics of this sort of diode regulator tube is given in Fig.2 to which reference is now had. The curve of Fig. 2 is obtained by gradually increasing the applied voltage in a simple series resistance circuit such as that of Fig. 3. The voltage across the tube is plotted as the abscissa while a logarithmic plot of current is the ordinate. This curve, wavy as it is summarizes the behavior of the tube over a wide range.

In the initial region approximately between the points A and B, current through the tube rises slowly as the voltage applied to the series resistance and tube is increased. Conduction in this region represents background current due to undesired efiects such as cosmic ray activity and leakage ionization, such conduction is rather small.

The region from B to C represents a region of unity amplification, or constant current wherein the background electrons of A-B are collected, however additional ionization within the tube does not occur so that of necessity the voltage across the tube experiences practically the same variation as the voltage impressed 3 across the series combination of resistance and tube.

At point C the corona discharge region begins. An ionization action begins at this point which is known as Townsend avalanches. As the voltage across the tube is increased, background electrons providing the only current heretofore passing through the tube anode naturally attain higher and higher velocity before reaching the anode. At the C point, background or other electrons in the tube achieve suflicient velocity as they approach the anode, that upon collision with a neutral atom or molecule of gas within the tube, they knock an electron out of the atom or molecule leaving the atom or molecule with a positive charge and provide two electrons traveling toward the anode. .Again if either of these two electrons achieves sufficient velocity and encounters another atom or molecule of the gas, an additional electron may be produced. Such multiplication will continue until electrons produced reach the anode. The rising portion from C to D indicates that as the voltage across the tube increases, electrons achieve sufficient velocity for Townsend avalanche activity to take place at a greater distance from the anode so that a greater number of electrons is produced by each initial electron before the anode is reached.

As the voltage applied across the series combination is increased further, the tube experiences an unstable conductivity region from D to E wherein a transition takes place from the corona region of Townsend avalanches to the lower voltage, constant voltage region of the glow discharge as characterized by high secondary emission current from the-cathode of the tube.

It is in this high current, low voltage region that acteristic, the structure of the electrodes, their r spacing and their length will affect the operation of the tube somewhat. Actually, I have found that for best corona operation the cathode to anode radius ratio should be as small as possible and approach or only slightly exceed the Napierian logarithm base 6. This radius of curvature limitation is imposed by the necessity of obtaining a suitable distribution of the field intensity to permit corona action.

Illustrative of the voltage regulator circuits with which the apparatus thus far discussed may be employed are those conventional circuits of Figs. 3 and 4. Fig. 3 shows a pair of input terminals l6 and. I1 across which an input unregulated voltage which may be typically in the region of 1000 volts is applied. For purposes of illustration the terminal [6 may receive the positive voltage while terminal I! receives the negative. The regulator tube is connected in series with resistance l8 across terminals [6 and I! with its anode [9 connected directly to resistance H3. The output voltage which is desired to be maintained constant despite fluctuations of the input voltage and output current, is obtained bttween terminals l7 and 20 across tube l0. Since the current capability of the regulator tube It) is quite limited and the voltages employed are usually high it is necessary that the load connected between terminals 20 and i! be of a very high impedance nature and ordinarily the resistance l8 will also be large, typically between one megohm and one hundred megohms.

To permit regulated high voltage operation of a low impedance load connected to the output, the somewhat modified circuit of Fig. 4 is preferred. Again in this figure the input unregulated voltage is supplied to the terminals l6 and [1, terminal (6 receiving the positive voltage. The series resistance 18 is replaced by an electron tube 2i which is of the hard variety with anode conductivity variable with variations in potential diiierences between the grid 22 and the cathode 23. The regulator tube [0, having its anode i9 is connected in series with resistance 24 and the anode-cathode impedance of tube 2| across terminals 16 and H. The output voltage is realized across terminals 20 and H with connection of terminal 20 to cathode 23. In this circuit the non-linear regulator tube 10 attempts to maintain the grid 22 at a uniform potential despite fluctuations of applied voltage or output current, the resistance 24 being quite large, in the region of one to one hundred megohms. Thus any tendency toward variations of the potential of cathode 23 and hence the output potential resultant to load changes or supply voltage variations is opposed by degenerative action in tube 2: similar to well known cathode follower action. The operation of these regulator circuits is well known and is included here merely for reference.

In conventional regulator tubes and circuits of the type thus far described for high voltage operation, it has been common practice to employ a pure gas such as helium or hydrogen in the space separating the electrodes of the tube 10. When the tube is filled with a pure gas the range of input voltage variation is limited because the transition from the desired corona region to the low voltage, high current glow discharge region occurs at very low currents in the order of a few micro-amperes. Such action sometimes may be desirable for control purposes because potentially it permits extremely close regulation of output voltage. On the other hand the range over which the conductivity of the tube can vary and hence, through the linear dropping resistance as previously typified by numeral 18, compensate for variations in the input voltage or load current is small.

It has been found that the addition of impurities of an electro-negative nature which readily form negative ions extends the corona region C to D of Fig. 2 of a helium filled tube over a wide range of current and hence permits compensation for greater fluctuations in input voltage. It has also been found that hydrogen added in small quantities has a similar stabilizing action on a helium filled tube. The simple impurities of an electro-negative nature which may conveniently be added are nitrogen and oxygen. Thus a small quantity of one of the three readily obtainable simple gases, hydrogen, nitrogen and oxygen may be added as components of a gaseous medium which is predominately helium to increase the current capabilities of the corona region. The addition of these simple gases to the conventional pure helium filling raises the ignition voltage of the tube .5 somewhat at any selected pressure, however an extension of the corona range by a substantial amount results.

For the purposes of the present invention the meaning of the term simple chemically inert gas is herein defined. The simple limitation refers to the necessity for a material existing in a mono-atomic or di-atomic state. Typical of these simple materials could be H2, 02, N2, N0,

CO, the halogens, etc. Chemically inert, as used herein implies that the simple gas employed is stable under the conditions of operation of the tube and does not react with any of the elements with which it comes into contact. A chemically inert gas is selected for dilution of the helium since thereby is maintained the desirable constant or nearly constant gas composition. It is desirable to maintain the percentage of the impurity in the helium as near a constant, known amount as possible thus excluding materials which may decompose in the tube or combine with the helium filling or tube structure. Chemical inertness in this case does not exclude materials such as oxygen because after an initial oxidized film is formed on the surface of the typical electrode material, copper, further loss of oxygen from the gaseous filling in any appreciable amount does not occur. For the purposes of the present invention, with proper electrode materials, even the halogens may be considered chemically inert if after an initial aging period, changes in the composition of the gaseous filling stop. The limitation gas is not intended to exclude substances commonly thought of as existent in a vapor state, or which vaporize from a liquid state, or a solid state rather than normally existent in a gaseous state. For the purposes of the present invention the terms gas and vapor are synonymous.

Proportions in which the simple gases hydrogen, nitrogen and oxygen are added to the helium filling are of considerable importance. Satisfactory operation with oxygen and nitrogen requires that whichever of these impurities is employed be present to the extent of approximately of one percent by partial pressure. It is thus apparent that with a gas present in such a minute quantity, small losses such as by oxidation of either of the electrodes or of minute leakage will be considerable percentagewise. On the other hand hydrogen may be employed with concentrations as high as five percent by partial pressure and since hydrogen does not ordinarily combine with electrode metals such as copper or stainless steel to any appreciable extent, a very stable mixture with resultant stability of regulator tube operation is provided.

Fig. 5 has been included to show regulation characteristics for an actual tube having a filling material which is a typical mixture of ninety-five percent helium and five percent hydrogen at 310 millimeters of mercury pressure. This figure is a plot of voltage across the regulator tube such as would be obtained across terminals and I! of Fig. 3 as one coordinate and as the othercoordinate the current through the tube in microamperes. To show the ignition characteristics of a typical regulator tube when filled with a medium in accordance with the teachings of the present invention which is ninety-five percent helium and five percent hydrogen, Fig. 6 has been included. Fig. 6 is a plot of ignition or firing voltage of the tube as one coordinate with pressure expressed in centimeters of mercury as the other coordinate. The firing voltage is expressive of the point at which a corona discharge starts for a given pressure as the voltage applied to terminals I6, I! is raised and hence gives an indication of the regulated voltages possible in a typical tube employing such a filling material, it being merely necessary to adjust the pressure of the filling medium to select a desired output regulation voltage.

A typical tube which provided the data present in Fig. 5 and Fig. 6 had the following dimensions. Inside diameter of the outer conductor one inch. Outside diameter of the inner conductor inch. Effective length of the conductors 3 inches. Outer conductor copper, inner conductor stainless steel.

Although certain specific embodiments of this invention have been herein disclosed and described, it is to be understood that they are merely illustrative of this invention and modifications may, of course, be made without departing from the spirit and scope of the invention as defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a voltage regulator tube including an outer cathode member surrounding an anode member wherein the ratio of diameters is not less than and approaches the Napierian logarithm base, a filling medium for said tube consisting of helium in admixture with a small amount of a simple gas chemically inert with respect to the members under operating conditions.

2. In a voltage regulator tube including an outer cathode member surrounding an anode member wherein the ratio of diameters is not less than and approaches the Napierian logarithm base, a filling medium consisting of a mixture of simple gases predominantly of helium with approximately one-tenth of one percent of the simple gases oxygen and nitrogen by partial pressures.

3. In a voltage regulator tube including an outer cathode member surrounding an anode member wherein the ratio of diameters is not less than and approaches the Napierian logarithm base, a filling medium consisting of a mixture of simple gases predominantly of helium and up to about 5% hydrogen by partial pressures.

4. A voltage regulator tube comprising a sealed envelope containing at least a pair of electrodes and a filling medium consisting of a mixture of helium and a simple gas chemically inert with respect to the electrodes under operating conditions selected from the group consisting of oxygen, nitrogen and hydrogen wherein the partial pressure of the helium is at least 5. In an enclosed voltage regulator device of a type comprising a sealed envelope containing at least a pair of electrodes, a filling medium consisting of a mixture of helium and up to about 5% hydrogen by partial pressure.

6. In an enclosed voltage regulator device of a type comprising a sealed envelope containing at least a pair of electrodes, 2. filling medium consisting of a mixture of simple gases predominantly of helium with approximately one-tenth of one percent of the simple gases oxygen and nitrogen by partial pressures.

7. In a voltage regulator tube including an outer cathode member surrounding an anode member wherein the ratio of diameters is not less 12. 21: @221 ePPXQfiQb-Qi m9 Hakim-mm 9%!1932 bag, a ms s ium 9; sa ll ub qon ifiin eswntial y 04 el um: nA mi-xt m with; fi gnall ampuntr Of. imp e a+- Q Qm Q J X inert w th respect tothe mqar'nbel lsv under opexa tpmg condin r n v lt eg lat r 112 n lud n an outer cathode member surrounding an a nqd e m m wh i h ma ic o d am te a inq k tha n roaches he. N anq ariihm as llin m di m o id t be q nsz st n esspnt-ially ofhelium with approximately one: en hm rcent i e m le a sg n and; nitmssmbyw part a messu s- 9. In a voltaIg regulator tube inclqgijng qn i cat o e m m er: smlmin n anp R f-eras s: in i n e: filq Q i en UNlTIT Dr STATE$ TENT Number: Name Date $162,505 James June 13, 1,939 2,' 184=,84l Katsch Dec. 26, 1.939 2,-39h982. Salzberg Apr. 9, 1946 

